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Deep osteochondral lesions amenable to ACI ‘sandwich’ technique
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Treating symptomatic osteochondral defects is challenging, especially in young adults with deep (>8-mm to 10-mm deep), empty defects after osteochondritis dissecans or collapsed condyles secondary to avascular necrosis. For this population, osteoarthritis is inevitable if articular congruence is not restored. Fragment removal of an osteochondritis dissecans lesion produces an incongruous joint surface, which uniformly leads to OA. Once a femoral condyle with avascular necrosis collapses (Ficat stage 3), OA ensues. Moreover, once defects deepen to more than 8-mm to 15-mm deep and have associated subchondral cystic and sclerotic bone changes, restoration of the osteochondral unit requires bone and cartilage restoration.
Jones and Peterson developed and presented cases of the autologous chondrocyte implantation (ACI) “sandwich” technique in the early 2000s, as a single, open operative procedure that involves autologous bone grafting (ABG) and ACI. The cultured chondrocytes were separated from the ABG and marrow space by “sandwiching” the cells between two periosteal membranes on the surface as a single-stage autologous reconstruction of the osteochondral unit.
This article describes the ACI “sandwich” technique for the treatment of large, deep osteochondral defects of the knee.
Indications, contraindications
Indications for surgery included osteochondral defects that were larger than 2 cm2 in size and deeper than 8 mm to 10 mm, with symptoms that matched the defect location. Surgery was only indicated in patients who were resistant to nonoperative therapies.
Contraindications to surgery included inflammatory joint disease, unresolved or recent septic arthritis, metabolic or crystal disorders, avascular necrosis (AVN) secondary to steroid with multiple infarcts, alcohol, chemotherapeutic agents, sickle cell crisis, etc.
Surgical technique
Patients are evaluated with physical examination, radiography, CT, MRI and arthroscopy before treatment is considered.
Cartilage biopsy is then performed during which about 200 mg to 300 mg of articular cartilage is harvested from the non-weight-bearing area of the knee, usually from the superior to the lateral aspect of the intercondylar notch. The biopsy specimen is cryopreserved, and surgeons plan to perform the second-stage open implantation following in vitro expansion of the cells for 3 to 5 weeks.
Sources: Tim Bryant, BSN, and Takahiro Ogura, MD
After a medial or lateral parapatellar arthrotomy, the osteochondral defect is found (Figure 1). A high-speed bur, which is usually 8-mm diameter, is used to remove all subchondral sclerotic or necrotic bone back to healthy-appearing, spongy bone under constant irrigation (Figure 2). The base of the lesion is multiply drilled with a Kirschner wire to enhance blood supply to the ABG. Then, a 3-mm diameter bur is used to undermine the subchondral bone to secure the membrane when it is glued to the ABG (Figure 3).
Predisposing background factors
Overall, concomitant procedures to address the background factors are performed in the same surgical setting as the articular repair with ABG and ACI. Tibiofemoral malalignment of more than 2° to 3° from the neutral mechanical axis into the involved compartment is corrected with concomitant osteotomy, either via a distal femoral osteotomy or a high tibial osteotomy. If needed, patellofemoral maltracking is corrected with a tibial tubercle osteotomy and proximal soft tissue balancing, as necessary, to centralize patellar tracking.
For the bone grafting step of the procedure, autologous cancellous bone chips are harvested locally with a core reamer and the area is back-filled with cancellous allograft chips, bone from a closing wedge tibial osteotomy or with bone harvested from the iliac crest, when necessary. The autologous cancellous bone is morselized and impacted up to the level of the native subchondral bone plate (Figure 4).
Chondrocyte implantation
The first membrane is glued with Tisseel fibrin glue (Baxter Biosurgery) and a few tacking sutures are placed circumferentially, as needed, over the bone graft using a 6 resorbable suture and with the cambium layer facing out (Figure 5). The membrane is then covered with a neural patty, the leg is brought into full extension and the tourniquet is let down. The knee is gently flexed up, the neural patty is gently removed to ensure the base of the defect is dry and no marrow-derived blood is present. A second periosteal membrane is microsutured on the articular surface at intervals of 3-mm to 5-mm circumferentially with the cambium layer facing the defect (Figure 6). The margins are then sealed watertight with Tisseel fibrin glue and the autologous cultured chondrocytes are injected between the two membranes, where they are “sandwiched” between the cambium layers of the periosteum. More recently, collagen membranes have been used in place of the periosteal patch in this step. The Bio-Gide (Geistlich Pharma) type I/III bilayer collagen membrane, derived from porcine peritoneum and skin, was used with this technique after May 2007.
Close the wound in layers and apply a soft dressing to the knee.
Pearl and pitfalls
Sandwich ACI provides durable hyaline repair tissue when patients are carefully chosen and background factors for the osteochondral defect are addressed surgically at the time of the sandwich ACI. This treatment offers patients native joint preservation for a condition that naturally will progress to OA and require prosthetic arthroplasty by restoring joint congruence and the osteochondral unit. Early use of a continuous passive-motion machine is recommended to promote cartilage repair. However, early weight-bearing can cause graft delamination. If weight-bearing causes any symptoms, including discomfort, catching, locking or swelling of the knee, the patient’s weight-bearing status and activity should be decreased to a level the patient can tolerate.
- References:
- Ficat RP, Arlet J. Necrosis of the femoral head. In: Hungerford DS, eds. Ischemia and Necrosis of Bone. Baltimore, MD: Williams & Wilkins, 1980; 171-182.
- Jones D, et al. Instr Course Lect. 2007;56:429-445.
- Linden B. J Bone Joint Surg Am. 1977;59:769-776.
- Minas T, et al. Am J Sports Med. 2017:doi:10.1177/0363546517738000.
- Sanders TL, et al. Am J Sports Med. 2017;doi:10.1177/0363546517699846.
- For more information:
- Tim Bryant, BSN, and Tom Minas, MD, MS, can be reached at Cartilage Repair Center, The Paley Institute, St. Mary’s Hospital, 901 45th St., Kimmel Building, West Palm Beach, FL 33407. Bryant’s email: tbryant@cartilagerepaircenter.org; Minas’ email: tminas@cartilagerepaircenter.org.
- Takahiro Ogura, MD, can be reached at Funabashi Orthopedic Hospital, 1-833 Hazama Funabashi, Chiba 274-0822 Japan; email: togura@fff.or.jp.
Disclosures: Minas reports he is a consultant for Vericel. Bryant and Ogura report no relevant financial disclosures.